Air-hydrate crystals in deep ice-core samples from Vostok Station, Antarctica

• Main Authors: Uchida, T., Hondoh, T., Mae, S., Lipenkov, V. Ya., Duval, P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: International Glaciological Society
• Subjects: 450; Greenland; Vostok Station; Antarc*; Antarctica; Dye 3; Dye-3; ice core; Ice Sheet; Journal of Glaciology
• Online Access: http://hdl.handle.net/2115/35167

Microscopic observation of air-hydrate crystals was carried out using 34 deep ice-core samples retrieved at Vostok Station, Antarctica. Samples were obtained from depths between 1050 and 2542m, which correspond to Wisconsin/Sangamon/Illinoian ice. It was found that the volume and number of air-hydrate varied with the climatic changes. The volume concentration of air-hydrate in the interglacial ice was about 30% larger than that in the glacial ice. In the interglacial ice, the number concentration of air-hydrate was about a half and the mean volume of air-hydrate was nearly three times larger than that in the glacial-age ice. The air-hydrate crystals were found to grow in the ice sheet, about 6.7×10^-12cm^3 year^-1, in compensation for the disappearance of smaller ones. The volume concentration of air-hydrate was related to the total gas content by a geometrical equation with a proportional parameter α. The mean value of α below 1250m, where no air bubbles were found, was about 0.79. This coincided with an experimentally determined value of the crystalline site occupancy of the air-hydrate in a 1500m core obtained at Dye 3, Greenland (Hondoh and others, 1990). In the depth profile of calculated α for many samples, α in the interglacial ice was about 30% smaller than that in the glacial-age ice.